complete failure of configure for autoconf-2.53.

[Stefan `Sec` Zehl]

The configure script of autoconf-2.53 is broken, as it makes a wrong
assumption about shells.  I hope you will fix that.

My system is a standard FreeBSD-4.6 with the following installed:
"/usr/local/bin/ksh" which is
ksh93-20020317      Official AT&T release of KornShell 93

As the standard FreeBSD /bin/sh does not support $LINENO, configure then
tries random shells to see if they do. The first that does is indeed
"/usr/local/bin/ksh"

configure then re-execs itself in ksh.

(IMHO that re-execing with a random shell is a bad idea in itself)

This ksh does search '.' when its PATH contains an invalid element. To
wit:

| ice:/usr/ports/devel/autoconf>/usr/local/bin/ksh
| $ cat conftest.sh
| #! /bin/sh
| echo got called
| exit 0
| $ ls -l conftest.sh
| -rwxr-xr-x  1 root  wheel  36 Jul 21 20:41 conftest.sh

| $ PATH=/bin
| $ conftest.sh
| /usr/local/bin/ksh: conftest.sh: not found
| $ PATH=foobar
| $ conftest.sh
| got called
| $ PATH=".;."
| $ conftest.sh
| got called

This makes the Test at line 90 go wrong and configure sets
PATH_SEPERATOR to ';' and later on fails spectacularly.

Please Fix.

CU,
    Sec
-- 
perl -nle 'print "$_ is divisible by 7" if (unpack("B*",reverse pack("L",$_))=~
/^0*((1((0(01|1(001*0)*11)*(00|1(001*0)*10))|1(01*0(1(10)*11)*0)*01*0(1(10)*
11)*1(10)*0)*(1(01*0(1(10)*11)*0)*1|0(01|1(001*0)*11)*1(001*0)*01))0*)+$/x)'